Multilayer heat rejection coating

Abstract

There is provided a multilayer coating comprising a plurality of layers comprising a) one or more layers of an elemental transition metal; b) one or more layers of an elemental metalloid; and c) two or more layers of an oxide; characterized in that the transition metal and metalloid layers are between the oxide layers and the plurality of layers does not need to contain an additional transparent conductive film (TCF). The multilayer coatings show high transparency in the visible light range combined with heat shielding without the need of transparent conductive oxide which have been previously used to achieve these properties. The multilayers can be produced with conventional physical vapor deposition methods on glass and polymer substrates. The coatings may therefore be used for applications on windows, plastic sheets and window shields. The invention relates also to the process for making the multilayer coatings, articles comprising them and their use in building and other applications.

What is claimed is: 
     
       1. A multilayer heat rejection coating comprising a plurality of layers comprising:
 one or more layers of elemental silver; 
 layers of elemental germanium; and 
 two or more layers of silicon dioxide (SiO 2 ); 
 wherein the silver and germanium layers are between the SiO 2  layers, 
 wherein a first layer of germanium is positioned on top of the silver layer and a second layer of germanium is positioned at the bottom of the silver layer, 
 wherein a first layer of SiO 2  is positioned on top of the outer germanium layer and a second SiO 2  layer is positioned at the bottom of the inner germanium layer of the coating, and 
 wherein the plurality of layers does not contain a transparent conductive oxide. 
 
     
     
       2. The multilayer coating of  claim 1 , comprising a multilayer consisting of SiO 2 /Germanium/Silver/Germanium/SiO 2 . 
     
     
       3. The multilayer coating of  claim 1 , wherein the coating consists of five to six layers. 
     
     
       4. An article comprising:
 a substrate; and 
 a multilayer coating of  claim 1  in the form of a multilayer on a surface of said substrate. 
 
     
     
       5. The article of  claim 4 , wherein the multilayer coating has a thickness in the range of 50 nm to 300 nm. 
     
     
       6. The article of  claim 4 , wherein the substrate is selected from materials in the group consisting of polymer, glass, wood, silicon, metal, metal alloy, and any mixture thereof. 
     
     
       7. The article of  claim 4 , further comprising a functional layer deposited on the multilayer coating. 
     
     
       8. The article of  claim 7 , wherein the functional layer is a self-cleaning layer comprising titanium dioxide. 
     
     
       9. The multilayer coating according to  claim 1  for use as a coating for windows, windshields, plastic sheets, or building materials. 
     
     
       10. A process for making a multilayer coating of  claim 1 , comprising depositing the layers using physical vapour deposition.